I don't think the limestone gravel would be helping those plants either. Is there any way you could re-arrange the system so that the water gets cycled past the plants before it goes through the limestone?
Not good about having got Dengue. We don't have it here and the authorities are vigilant in stopping it coming in. They have it over to the east so it is on our "door step". We do have Ross River but I'm lucky because I have some sort of immunity to it. Don't think it works that way with Dengue (and I'd rather not find out).
